1. Field of the Invention
The present invention relates to an apparatus for driving a light emitting diode (LED) that distributes current stress applied to the LED.
2. Description of the Related Art
Recently, interest and demand for light emitting diodes (LEDs) has increased.
Devices using LEDs can be manufactured to be compact so that they can be used in situations in which it is difficult to install existing electronic products. In a case in which an LED is used as an illumination device, various colors of light may be implemented in the illumination device, and the intensity of illumination may be controlled, such that LED illumination devices can be used as system illumination devices suitable for use in activities such as watching movies, reading books, conferencing, etc.
Also, LED power consumption is approximately ⅛ that of light bulbs, and a lifespan thereof is 50,000˜100,000 hours, approximately 5˜10 times that of light bulbs . LEDs are light sources that do not contain mercury, are environmentally-friendly, and are capable of being implemented in various designs.
Owing to such characteristics, many countries such as the United States, Japan, Australia, and others, including Korea, have promoted LED illumination development programs as national enterprises.
In addition, recently, as flat panel display (FPD) technology has been developed, an FPD has been used for a vehicle gauge in addition to having applications in smartphones, game machines, and digital cameras. In the future, the FPD will have a wide range of applications to appliances for every-day use such as ultrathin televisions and transparent navigation systems. In the current display industry, the main market is for FPD products incorporating new technologies reflecting demands stemming from the multimedia era for displays incorporating high resolution and large screens. In particular, in the large display market, sales of liquid crystal display (LCD) televisions have seen rapid growth and thus, LCD TVs are expected to play a leading role in terms of setting future prices and determining marketability.
A thin film transistor liquid crystal display (TFT-LCD) is a main component in FPDs. Such a TFT-LCD includes a backlight unit that emits light and mainly uses a cold cathode fluorescent lamp (CCFL) as a backlight source. However, there has been a recent tendency for the use of LEDs therein owing to various LED characteristics in terms of power consumption, lifespan, and environmental-friendliness. Thus, construction of a low-priced electronic power system of a backlight unit power module using an LED and an appropriate control element thereof are urgently required.
As described above, LEDs, the use of which is increasing, require an apparatus for the driving thereof and an appropriate power source. In a case in which the LED is used by generating direct current (DC) power from alternating current (AC) power, a converter circuit for supplying the DC power is needed, leading to a circuit being complicated. Even in a case in which a simple rectifier is used, an electrolytic capacitor that may reduce the lifespan of the entire system is needed, and a power factor may be problematically reduced.
Accordingly, as disclosed in the related art document below, although a method of driving the LED by directly using power rectified from alternating current power is disclosed, there are defects in that voltage magnitude of the rectified power may vary in the manner of a sine wave, and current stress may be applied excessively to a specific LED according to the varied voltage.